Bruise? Yeah, I've got more to say.
A couple of threads ago I slugged the bores of the two SKS's that I currently own, a late nineties Norinco and a Yugo milsurp that was made God knows when. (As I understand it, Zastava is still cranking these suckers out.) The Norinco slugged out at .001" over nominal, the Yugo .002". The Yugo is the better shooter. Neither is a tack driver but the Yugo is acceptable.
My quick-and-dirty method of judging acceptable accuracy is to sight it at 100, confirm at 150/200, and go to the plates. The plates are 8" or so and are about 180 yards away. I ought to be able to thump them with a six o'clock hold with the sights set on 200. If the sights don't jive I'll play around with the hold until I figure it out. A rifle should reliably produce clangs from the bench, prone, or sitting. That's my standard. Other people have other standards. An SKS in good repair, with a good barrel and ammunition that it likes, can do this.
Consistancy = accuracy. If everything is the same every time, we'll hit every time. Improving accuracy is the process of removing variables. Some of them are ammunition variables, some of them are rifle variables, and some of them (all too often, at least in my case) are shooter variables. We need to do everything the same way every time, or as close to this as we can manage. Removing variables should be the first step in troubleshooting a rifle that isn't shooting as well as we think that it should.
So...
Stop adjusting the rear sight in the middle of the string. Get yourself a front sight adjustment tool (or improvise one) and zero the weapon at 100. The SKS sights are graduated in meters. My range (and your range as well, it seems) is graduated in yards. 100 meters = 110 yards, give or take, so the difference is not really significant at the sort of ranges that an SKS is normally fired at. Dial it in at 100, set the rear for 200, and try the target again. If the results are not satisfactory, try using the 100 or 300 settings with the appropriate hold. Once you've got that figured out, shoot from the bench or prone (don't be afraid of using the sling here) and fire a group for score. Fire groups of 3-5 rounds; more than that shifts the workload from the rifle to the shooter. Call the fliers. Call the hits. If possible, have someone spotting the shots.
If it still doesn't shoot right? We have other things that we can look at.
Everyone owns, or knows someone who owns, a given rifle that produces 1-2 MoA with a given brand of ammunition. The only ones that I actually see doing this on a regular basis are the ones that cost a lot of money and are fed the right kind of ammunition. Milsurps are a bargain, don't get me wrong, but we're sometimes left with unrealistic expectations of what they can do. If every Mauser/SKS/AK/Enfield/M-N/whatever produced 1 MoA reliably, there would be no market for high end firearms.